JP6449114B2 - Wireless communication method and wireless communication system - Google Patents

Description

  The present invention relates to a wireless communication method and a wireless communication system in which a first wireless station and a plurality of second wireless stations are connected, and the first wireless station controls transmission timing of the second wireless station.

  In a wireless LAN system, a base station and a terminal connected to the base station perform wireless communication using one or a plurality of frequency channels set by the base station. Since the number of frequency channels that can be used by the wireless LAN system is limited, when a plurality of base stations are installed close to each other, the same frequency channel is used by the plurality of base stations. Even when a large number of terminals are connected to one base station, each terminal transmits a radio signal using a frequency channel set by the base station. The terminal will use it. Therefore, in an environment where a plurality of base stations exist and a plurality of terminals are connected under the base station, communication in the same frequency channel is crowded, and the base station and the terminal may try to transmit at the same timing. To increase. As a result, transmission signal collisions frequently occur. The increase in collisions causes a loss of radio signals and an increase in overhead time for transmission, which causes a reduction in throughput characteristics of the entire system.

  For such a problem, there is a centralized control method in which a base station sequentially gives transmission rights to subordinate terminals (Non-Patent Document 1). Since the terminal does not transmit unless the transmission right is given from the base station, the above-described collision does not occur.

FIG. 9 shows a radio access control system described in Non-Patent Document 1.
In FIG. 9, when the base station permits the terminal 1 to transmit, a polling frame is transmitted to the terminal 1. The polling frame describes a NAV (Network Allocation Vector) period for prohibiting transmission except for the destination terminal. The terminal 2 that has received the polling frame addressed to the terminal 1 does not transmit during the NAV period described in the polling frame. The terminal 1 transmits a data frame to the base station during the NAV period. The base station that has received the data frame from the terminal 1 returns an ACK frame to the terminal 1. After the NAV period set for the terminal 2 elapses, the base station transmits a polling frame again. Next, when transmission of the terminal 2 is permitted, a NAV period is set for the terminal 1. The terminal 2 transmits a data frame to the base station using the period. Thereby, characteristic deterioration due to collision can be reduced.

  In addition, a terminal grouping method for reducing the above-described collision has been proposed (Patent Document 1, Non-Patent Document 2). In this method, the base station groups the terminals under its control and gives a transmission right to each terminal group. Transmission control of terminals in each group is performed based on CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance), which is an autonomous distributed access control method adopted by the wireless LAN system. Thereby, since the transmission right is given for each terminal group determined by the base station, it is possible to suppress the number of terminals trying to transmit at the same time, and to reduce collision as a result.

FIG. 10 shows a radio access control method described in Patent Literature 1 and Non-Patent Literature 2.
In FIG. 10, it is assumed that terminals 1 to 3 are set as a terminal group # 1 and terminals 4 to 5 are set as a terminal group # 2 by the base station in advance. When the base station grants transmission permission to terminals belonging to the terminal group # 1, a control frame (CTS-to-group #) in which an address indicating the terminal group # 1 and a period during which terminals belonging to the terminal group # 1 can transmit is described. 1) Send. The terminals 4 to 5 belonging to the terminal group 2 that have received the control frame do not transmit during the period described in the control signal (NAV period). During this period, the terminals 1 to 3 belonging to the terminal group # 1 transmit data frames while performing transmission control based on CSMA / CA.

  When the base station grants transmission permission to terminals belonging to terminal group # 2 after the end of the period, a control frame (CTS−) that describes an address indicating terminal group # 2 and a period during which terminals belonging to terminal group # 2 can transmit. to-group # 2). Similarly, the terminals 4 to 5 belonging to the terminal group # 2 that received the control frame transmit the data frame while performing transmission control based on CSMA / CA. Thereby, since the number of terminals to be transmitted simultaneously can be reduced, characteristic deterioration due to collision can be reduced. Further, by giving a transmission opportunity to a plurality of terminals, the possibility that a data frame is transmitted within the transmission period given from the base station is higher than that in the wireless access control method of Non-Patent Document 1, The waste of time can be suppressed. In addition, by grouping for each terminal standard, there is an effect that the influence due to the performance difference according to each standard can be reduced.

Japanese Patent Laying-Open No. 2015-026935

IEEE Standard for Local and Metropolitan Area Networks Part 11: Wireless LAN MAC and PHY Specifications, 2012. Toshiyuki Shintaku, Akira Kishida, Atsushi Iwasaki, Takeshi Onizawa, Tohru Sakata, “Experimental study of QoS control method using terminal grouping according to wireless LAN standards”, IEICE, IEICE Technical Report, April 2014

  In the radio access control method using the polling frame shown in FIG. 9, a transmission period is given to each terminal in turn, but when the base station gives a transmission period to the terminal, there is no data to be transmitted to the terminal. The transmission period is wasted. As a result, the throughput characteristics of the entire system are degraded.

  Further, in the radio access control method by terminal grouping shown in FIG. 10, the terminal can transmit only in the transmission period assigned to the terminal group determined by the base station, and transmission delay tends to occur. This problem of transmission delay is the same in the radio access control method shown in FIG.

  An object of the present invention is to provide a radio communication method and a radio communication system capable of suppressing waste of time resources as much as possible, suppressing transmission delay of a terminal, and reducing influence due to a difference in terminal performance while reducing collisions. And

According to a first aspect of the present invention, there is provided a wireless communication method in which a first wireless station is connected to a plurality of second wireless stations, and the first wireless station controls transmission timing of the second wireless station. Is a step of periodically transmitting a transmission policy indicating a condition that the second wireless station may transmit according to its communication state and a notification signal for notifying a period during which transmission is prohibited (hereinafter referred to as a period). It has a second radio station receives the notification signal, for each a period, a first determining transmittable or transmission inhibited communication state of the own station by whether satisfies the transmission policy The wireless station that has been determined to be able to transmit according to the transmission policy performs a transmission process within the period a, and the wireless station that has been determined to be prohibited from transmission has a second step of performing control to refrain from transmission within the period a.

According to a second aspect of the present invention, there is provided a wireless communication method in which a first wireless station is connected to a plurality of second wireless stations, and the first wireless station controls transmission timing of the second wireless station. Is a step of periodically transmitting a transmission policy indicating a condition that the second wireless station may transmit according to its communication state and a notification signal for notifying a period during which transmission is prohibited (hereinafter referred to as a period). The second wireless station receives the notification signal, and performs a process of determining whether transmission is possible or transmission prohibited depending on whether the communication state of the local station satisfies the transmission policy within the period a. The first step that is performed a plurality of times, and the radio station that is determined to be transmittable in accordance with the transmission policy performs transmission processing within the period b, and the radio station that is determined to be prohibited from transmission performs control to refrain from transmission within the period b And a first step every period a. And repeating the second step.

In the wireless communication method of the first or second invention, the second wireless station may receive the CSMA before the notification signal is notified, when the notification signal is not notified, or when transmission is possible. Control transmission using the / CA method.

A third invention is a wireless communication system in which a first wireless station is connected to a plurality of second wireless stations, and the first wireless station controls transmission timing of the second wireless station. Means for periodically transmitting a transmission policy indicating a condition that the second wireless station may transmit according to its communication state and a notification signal for notifying a period during which transmission is prohibited (hereinafter referred to as period a) comprising a second radio station receives the notification signal, for each a period, a first means for determining possible transmission or transmission inhibited communication state of the own station by whether satisfies the transmission policy, The wireless station that has been determined to be able to transmit in accordance with the transmission policy performs transmission processing within the period a, and the wireless station that has been determined to be prohibited from transmission includes second means for performing control to refrain from transmission within the period a.

A fourth invention is a wireless communication system in which a first wireless station is connected to a plurality of second wireless stations, and the first wireless station controls the transmission timing of the second wireless station. Means for periodically transmitting a transmission policy indicating a condition that the second wireless station may transmit according to its communication state and a notification signal for notifying a period during which transmission is prohibited (hereinafter referred to as period a) The second wireless station receives the notification signal, and performs a process for determining whether transmission is possible or transmission prohibited depending on whether the communication state of the local station satisfies the transmission policy within the period a. A first means that performs a plurality of times, and a radio station that has determined that transmission is possible according to the transmission policy performs transmission processing within period b, and a radio station that has determined transmission prohibition performs control to refrain from transmission within period b 2 means, and the first means and the second means every a period It repeats the processing of means.

In the wireless communication system of the third or fourth invention, the second wireless station may receive the CSMA before the notification signal is notified, when the notification signal is not notified, or when transmission is possible. This is a configuration for performing transmission control by the / CA method.

  According to the present invention, it is possible to reduce the number of terminals to be transmitted at the same time, thereby reducing collisions. In addition, since the terminal can perform transmission when the transmission policy specified by the base station is satisfied, it is possible to avoid wasting time resources without excessively limiting the transmission possible time of the terminal. It is also possible to suppress the transmission delay of the terminal by the transmission policy set by the base station, and by setting the transmission conditions that can be transmitted only by the terminal with the same performance or communication environment, the performance difference of the terminal Can also reduce the effects of

It is a figure which shows the Example structure of the radio | wireless communications system of this invention. It is a figure which shows the definition of each period used by this invention. It is a flowchart which shows the example of a process sequence of the base station and terminal in this invention. It is a figure which shows the state transition of a terminal. It is a time chart which shows the operation example 1 of the base station and terminal in this invention. It is a time chart which shows the operation example 2 of the base station and terminal in this invention. It is a figure which shows the apparatus structural example of a base station. It is a figure which shows the apparatus structural example of a terminal. 10 is a time chart showing a wireless access control method described in Non-Patent Document 1. 10 is a time chart showing a wireless access control method described in Patent Literature 1 and Non-Patent Literature 2.

FIG. 1 shows an embodiment of a radio communication system according to the present invention.
In FIG. 1, the wireless communication system includes a base station 10 and terminals 11 to 14. Note that the present invention can be applied to any number of base stations and terminals.

  Terminals 11 to 14 are connected to the base station 10 and communicate with the base station 10. In the embodiments described below, it is assumed that uplink communication from a terminal to a base station. The present invention can also be applied to downlink communication from a base station to a terminal. In that case, the base station has the function of a terminal described in this embodiment, and when the base station transmits, the base station transmits using the same transmission method as the terminal.

FIG. 2 shows the definition of each period used in the present invention.
In FIG. 2, a conditional transmission prohibition period (hereinafter referred to as “a period”) is a period in which transmission is refrained when the terminal does not satisfy a transmission policy (single or multiple conditions) specified by the base station, It is notified by a notification signal from the base station to the terminal. In the period a, a period shorter than the period from the transmission of the notification signal to the transmission of the next notification signal is set.

  The determination cycle (hereinafter referred to as “b period”) is a time cycle for determining whether or not the terminal satisfies the transmission policy notified from the base station, so that at least two determinations can be made in a period shorter than the a period. Is set. The period b may be set in advance by the terminal, or may be dynamically set according to the transmission policy notified from the base station and the period a. It may be set so that the period b is not provided.

FIG. 3 shows an example of processing procedures of the base station and terminal in the present invention.
FIG. 4 shows the state transition of the terminal.
In FIG. 3 (1), the base station 10 determines a transmission policy and a conditional transmission prohibition period (a period (S11). Here, the transmission policy is a condition that the terminal may transmit. required bandwidth but to request (communication speed, throughput), the transmission rate in the terminal, the carrier sense level, the received power of the transmission power, signal sent from the base station, the end end of the application, the application, other base stations and radio communication in a terminal The parameter used for.

  Next, the base station 10 transmits a notification signal carrying the transmission policy and the information of the period a to surrounding terminals (S12). As a notification method, a broadcast signal may be used for the whole, a multicast signal may be used for a specific group of terminals, or a unicast signal may be used for a specific terminal.

  After elapse of the period a set by itself, the base station 10 determines the transmission policy and the period a again, and similarly repeats the operation of transmitting to neighboring terminals (S11 to S13).

  3 (2) and 4, the terminals 11 to 14 are in a normal state (FIG. 4: S100) until receiving a notification signal from the base station, and execute normal transmission control by CSMA / CA (S21, S100). S22). If the terminal receives a notification signal from the base station 10 but is not a terminal subject to notification of the transmission policy and period a, the terminal transits to a transmission ready state (FIG. 4: S101), and the normal CSMA / CA Transmission control is continued, and the normal state (FIG. 4: S100) returns after the elapse of the period a.

  If the terminals 11 to 14 receive the notification signal from the base station 10 and are terminals to be notified (S22: Yes), the terminals 11 to 14 transition to the pre-determination state (FIG. 4: S201) and enter the period a and the determination cycle ( b period) is set (S23). Then, it is determined whether or not a period has elapsed since the reception of the notification signal (S24). If the a period has elapsed, the process returns to the normal state (FIG. 4: S100), and if within the a period, the determination state ( FIG. 4: The process proceeds to S202), where it is determined whether or not the current communication state of the terminal satisfies the transmission policy (S25).

  When the communication state satisfies the transmission policy, the terminals 11 to 14 transition to the conditional transmission enabled state (FIG. 4: S203) and execute transmission control by CSMA / CA (S26). On the other hand, if the transmission policy is not satisfied, the state transits to the conditional transmission prohibited state (FIG. 4: S204) and transmission is refrained (S27). The determination of the transmission policy is repeated every time the b period elapses within the period a (S28, S24), and depending on whether the communication state of the terminal satisfies the transmission policy, a conditional transmission possible state (FIG. 4: S203) or conditional transmission prohibited state (FIG. 4: S204) is selected.

  The terminals 11 to 14 determine whether or not the period a has elapsed when the conditional transmission enabled state or the conditional transmission prohibited state is selected according to the communication state and transmission policy of the terminal every b period. (S28, S24) When the period a has elapsed, the process returns to the normal state (FIG. 4: S100) and waits for reception of a new notification signal (S21, S22).

  FIG. 5 shows a first operation example of the base station and the terminal according to the present invention. S100 and S201 to S204 shown here correspond to the transition state of the terminal shown in FIG. S001 corresponds to the state of the base station.

  The base station 10 determines a transmission policy and a period, and notifies the determined information to the terminals 11 to 14 by a notification signal (S001). The terminals 11 to 14 are in a normal state (S100) until notified.

  The terminals 11 to 14 that have received the notification pass through the pre-determination state (S201) and the determination state (S202), and the terminals 11 and 12 whose communication state satisfies the transmission policy transit to the conditional transmission enable state (S203). Transmission starts based on CSMA / CA. On the other hand, the terminals 13 and 14 whose communication state does not satisfy the transmission policy transit to the conditional transmission prohibited state (S204) and refrain from transmission. Thereby, a terminal satisfying the transmission policy can perform transmission with priority and efficiency.

  After the period a has elapsed, the terminals 11 to 14 transition to the normal state (S100). Thereafter, the base station 10 notifies the terminals 11 to 14 of the transmission policy and the period a by a notification signal (S001).

  The terminals 11 to 14 that have received the next notification signal go through the pre-determination state (S201) and the determination state (S202), and the terminals 13 and 14 whose communication state satisfies the transmission policy enter the conditional transmission ready state (S203). Transition and start transmission based on CSMA / CA. On the other hand, the terminals 11 and 12 whose communication state does not satisfy the transmission policy transit to the conditional transmission prohibited state (S204) and refrain from transmission. Thereby, a terminal satisfying the transmission policy can perform transmission with priority and efficiency.

  FIG. 6 shows an operation example 2 of the base station and the terminal in the present invention. S100 and S201 to S204 shown here correspond to the transition state of the terminal shown in FIG. S001 corresponds to the state of the base station.

  The base station 10 determines a transmission policy and a period, and notifies the determined information to the terminals 11 to 14 by a notification signal (S001). The terminals 11 to 14 are in a normal state (S100) until notified.

  The terminals 11 to 14 that have received the notification set the period b in the pre-determination state (S201), and further pass through the determination state (S202), and the terminals 11 and 12 whose communication state satisfies the transmission policy are in a conditionally transmittable state. The process proceeds to (S203), and transmission is started based on CSMA / CA. On the other hand, the terminals 13 and 14 whose communication state does not satisfy the transmission policy transit to the conditional transmission prohibited state (S204) and refrain from transmission.

  After the period b has elapsed, the terminals 11 to 14 again pass through the pre-determination state (S201) and the determination state (S202), and the terminals 11 and 12 whose communication state satisfies the transmission policy and the communication state satisfies the transmission policy. The terminal 13 which has decided to do so makes a transition to a conditional transmission enable state (S203) and starts transmission based on CSMA / CA. On the other hand, the terminal 14 whose communication state does not satisfy the transmission policy transits to the conditional transmission prohibited state (S204) and refrains from transmission.

  Further, after the elapse of the period b, the terminals 11 to 14 again pass through the pre-determination state (S201) and the determination state (S202), and the terminals 11 and 13 whose communication state satisfies the transmission policy are in the conditionally transmittable state (S203). ) To start transmission based on CSMA / CA. On the other hand, the terminals 12 and 14 whose communication state does not satisfy the transmission policy transit to the conditional transmission prohibited state (S204) and refrain from transmission.

  As described above, a terminal satisfying the transmission policy can perform transmission preferentially and efficiently every b period. Further, when the period a elapses, the terminals 11 to 14 transition to the normal state (S100), and the base station 10 notifies the terminals 11 to 14 of the transmission policy and the period a by a notification signal and repeats the above processing.

FIG. 7 shows a device configuration example of the base station 10 in the present invention.
In FIG. 7, the antenna unit 21 receives radio waves and transmits them to the transmission / reception processing unit 22. In addition, the transmission data generated by the transmission / reception processing unit 22 is emitted to the outside as radio waves. The transmission / reception processing unit 22 converts the radio wave input from the antenna unit 21 into baseband, and demodulates it by signal processing. Data input from the transmission control unit 23 is modulated and up-converted and transmitted from the antenna unit 21.

  Of the data obtained by demodulation by the transmission / reception processing unit 22, data necessary for determining the transmission policy is processed by the transmission policy determination unit 24, and other data is transferred to the upper network 25. As a transfer method, Ethernet (registered trademark) may be used, an optical fiber may be used, or a separate wireless method may be used.

  The transmission control unit 23 determines whether to transmit data. The transmission control method in the transmission control unit 23 may be any method. For example, transmission control based on CSMA / CA is performed. The transmission control unit 23 outputs data to the transmission / reception processing unit 22 based on the transmission control method provided when there is data to be transmitted to the transmission policy determination unit 24 and the buffer unit 26.

  The buffer unit 26 stores transmission data input from the network 25. The buffer unit 26 operates in conjunction with the transmission control unit 23 and outputs data stored at the transmission timing determined by the transmission control unit 23 to the transmission / reception processing unit 22.

  The transmission policy determination unit 24 determines a transmission policy and a period to be notified to the terminal, generates a notification signal for transmitting the transmission policy and the a period to the terminal, and outputs the notification signal to the transmission control unit 23.

FIG. 8 shows a device configuration example of the terminals 11 to 14 in the present invention.
In FIG. 8, the antenna unit 31 receives radio waves and transmits them to the transmission / reception processing unit 32. In addition, the transmission data generated by the transmission / reception processing unit 32 is emitted to the outside as radio waves. The transmission / reception processing unit 32 converts the radio wave input from the antenna unit 31 into a baseband and demodulates it by signal processing. The data input from the transmission control unit 33 is modulated and up-converted and transmitted from the antenna unit 31.

  Of the data obtained by demodulation by the transmission / reception processing unit 32, data for determining the transmission policy is processed by the transmission policy determination unit 34, and other data is transferred to the upper layer 35.

  The transmission control unit 33 determines whether to transmit data according to the determination result of the transmission policy determination unit 34. The transmission control method in the transmission control unit 33 may be any method. For example, transmission control based on CSMA / CA is performed. When there is data to be transmitted in the buffer unit 36, the transmission control unit 33 outputs the data to the transmission / reception processing unit 32 based on the provided transmission control method.

  The buffer unit 36 stores transmission data input from the upper layer 35. The buffer unit 36 operates in conjunction with the transmission control unit 33 and outputs data stored at the transmission timing determined by the transmission control unit 33 to the transmission / reception processing unit 32.

  The transmission policy determination unit 34 compares the transmission policy notified from the base station with its own communication state, and determines whether or not the transmission policy is satisfied. If the result of determination is that transmission is possible, the transmission control unit 33 is notified accordingly. If the transmission is prohibited, the transmission control unit 33 is notified of this. Although the transmission policy determination unit 34 manages the determination timing (period b), a predetermined value may be used or may be changed dynamically.

DESCRIPTION OF SYMBOLS 10 Base station 11-14 Terminal 21, 31 Antenna part 22, 32 Transmission / reception processing part 23, 33 Transmission control part 24 Transmission policy determination part 25 Network 26, 36 Buffer part 34 Transmission policy determination part 35 Upper layer

Claims (6)

In a wireless communication method in which a first wireless station is connected to a plurality of second wireless stations, and the first wireless station controls transmission timing of the second wireless station,
The first radio station transmits a transmission policy indicating a condition that the second radio station may transmit according to its communication state, and a notification signal for notifying a period during which transmission is prohibited (hereinafter referred to as a period). And periodically sending
The second radio station is
Receiving the notification signal, for each of the a period, a first determining transmittable or transmission inhibited communication state of the own station by whether satisfies the transmission policy,
A radio station that has determined that transmission is possible with respect to the transmission policy performs a transmission process within the period a, and a radio station that has determined that transmission is prohibited has a second step of performing control to refrain from transmission within the period a. A wireless communication method. In a wireless communication method in which a first wireless station is connected to a plurality of second wireless stations, and the first wireless station controls transmission timing of the second wireless station,
The first radio station transmits a transmission policy indicating a condition that the second radio station may transmit according to its communication state, and a notification signal for notifying a period during which transmission is prohibited (hereinafter referred to as a period). And periodically sending
The second radio station is
Receiving the notification signal, in the a period, a first step a plurality of times a process of determining a transmittable or transmission prohibition every b period communication state of the own station by whether satisfies the transmission policy When,
A radio station that has determined that transmission is possible according to the transmission policy performs a transmission process within the period b, and a radio station that has determined that transmission is prohibited has a second step of performing control to refrain from transmission within the period b. And
The wireless communication method , wherein the first step and the second step are repeated every a period . The wireless communication method according to claim 1 or 2 ,
The second radio station performs transmission control by the CSMA / CA method before the notification signal is notified, when the notification signal is not notified, or when transmission is possible. A wireless communication method characterized by the above. In a wireless communication system in which a first wireless station and a plurality of second wireless stations are connected, and the first wireless station controls transmission timing of the second wireless station,
The first radio station transmits a transmission policy indicating a condition that the second radio station may transmit according to its communication state, and a notification signal for notifying a period during which transmission is prohibited (hereinafter referred to as a period). Has a means to periodically send
The second radio station is
Receiving the notification signal, for each of the a period, a first means for determining possible transmission or transmission inhibited communication state of the own station by whether satisfies the transmission policy,
A wireless station that determines that transmission is possible with respect to the transmission policy performs a transmission process within the period a, and a wireless station that determines that transmission is prohibited includes a second unit that performs control to refrain from transmission within the period a. A wireless communication system characterized by the above. In a wireless communication system in which a first wireless station and a plurality of second wireless stations are connected, and the first wireless station controls transmission timing of the second wireless station,
The first radio station transmits a transmission policy indicating a condition that the second radio station may transmit according to its communication state, and a notification signal for notifying a period during which transmission is prohibited (hereinafter referred to as a period). Has a means to periodically send
The second radio station is
Receiving the notification signal, the within a period, first means for performing a plurality of times a process of determining a transmittable or transmission prohibition every b period communication state of the own station by whether satisfies the transmission policy When,
A radio station that has determined that transmission is possible with respect to the transmission policy performs a transmission process within the period b, and a radio station that has been determined to be prohibited from transmission includes second means for performing control to refrain from transmission within the period b. Huh,
A wireless communication system, wherein the processing of the first means and the second means is repeated every period a . The wireless communication system according to claim 4 or 5,
The second radio station performs transmission control by the CSMA / CA method before the notification signal is notified, when the notification signal is excluded from the notification signal, or when transmission is possible. A wireless communication system, characterized in that

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